Home wastewater treatment is an economical option for buildings which are located in areas without access to a city sewage system, or where the costs of hooking the building into a municipal sewage system are prohibitive. Home wastewater treatment systems perform similar functions as a sewage plant, but on a much smaller scale. These systems are typically located underground. After the wastewater has been treated it is typically discharged as waste on the property. It is essential that the wastewater is processed sufficiently so that the discharged water does not pose a threat to the environment.
In some geographical regions, wastewater discharged from a home wastewater treatment system—the wastewater effluent—must contain reduced nitrogen levels. When wastewater effluent contains excess amounts of nitrogen-based compounds, and when such wastewater effluent enters waterways, eutrophication, or hypertrophication can result. Eutrophication is the response of an ecosystem to excess artificial natural or artificial substances. One example of eutrophication is the increase of phytoplankton in a body of water, such increase can result in a “bloom” or bright green coloring of the water. Not only does eutrophication discolor the water, but it also disrupts the ecosystem, and can deplete the oxygen levels in the water, which in turn can cause natural species, such as fish, to reduce in numbers or die off.
There are several types of nitrogen which may be present in wastewater and which may need to be reduced, such as ammonia, nitrate, nitrite and organically-bound nitrogen. Total Kjeldahl Nitrogen (TKN) is a test method that measures the combination of organically-bound nitrogen and ammonia. Total Nitrogen (TN) is the sum of the TKN and nitrate and nitrite. To prevent eutrophication and other problems related to excess nitrogen, it is desired that the TN in the wastewater effluent is reduced. It is desired that the TN in the wastewater effluent be reduced by a minimum of 75% relative the TN of the wastewater influent.
One way to reduce nitrogen is through the use of a combination of aerobic and anaerobic bacteria. One suitable pathway of bacteria-aided nitrogen reduction is described as follows. The bacteria reduce ammonia to nitrite, and those or other bacteria reduce nitrite to nitrate, finally the nitrate is denitrified into molecular nitrogen, N2 by bacteria. The molecular nitrogen bubbles out of the system, which results in an overall reduction in the nitrogen content in the wastewater. The final step of denitrification generally requires anaerobic conditions, while the other steps typically require aerobic conditions. As such, the wastewater treatment system must be designed to oscillate between aerobic and anaerobic conditions such that all phases of the nitrogen-reduction process may be achieved.
At the same time, the wastewater treatment system must be suitable for performing its primary function, which is to process the waste found in the wastewater. Typically, such waste is processed by bacteria which gasify nitrogen compounds into atmospheric nitrogen and carbon compounds into carbon dioxide.
As such, an improved home wastewater treatment system is needed which is suitable to both process the waste in the wastewater and to reduce the TN in the wastewater.